Problem: Simplify the following expression: $k = \dfrac{c + 6b}{3a + 6c} - \dfrac{2c + 5a}{3a + 6c}$ You can assume $a,b,c \neq 0$.
Solution: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{c + 6b - (2c + 5a)}{3a + 6c}$ $k = \dfrac{-c + 6b - 5a}{3a + 6c}$